Recent advances toward defining the benefits and risks of erythrocyte transfusions in neonates

Thresholds for blood transfusion in extremely preterm infants: A review of the latest evidence from two large clinical trials

There are two recently completed large randomized clinical trials of blood transfusions in the preterm infants most at risk of requiring them. Liberal and restrictive strategies were compared with composite primary outcome measures of death and neurodevelopmental impairment. Infants managed under restrictive guidelines fared no worse in regard to mortality and neurodevelopment in early life. The studies had remarkably similar demographics and used similar transfusion guidelines. In both, there were fewer transfusions in the restrictive arm. Nevertheless, there were large differences between the studies in regard to transfusion exposure with almost 3 times the number of transfusions per participant in the transfusion of prematures (TOP) study. Associated with this, there were differences between the studies in various outcomes. For example, the combined primary outcome of death or neurodevelopmental impairment was more likely to occur in the TOP study and the mortality rate itself was considerably higher. Whilst the reasons for these differences are likely multifactorial, it does raise the question as to whether they could be related to the transfusions themselves? Clearly, every effort should be made to reduce exposure to transfusions and this was more successful in the Effects of Transfusion Thresholds on Neurocognitive Outcomes (ETTNO) study. In this review, we look at factors which may explain these transfusion differences and the differences in outcomes, in particular neurodevelopment at age 2 years. In choosing which guidelines to follow, centers using liberal guidelines should be encouraged to adopt more restrictive ones. However, should centers with more restrictive guidelines change to ones similar to those in the studies? The evidence for this is less compelling, particularly given the wide range of transfusion exposure between studies. Individual centers already using restrictive guidelines should assess the validity of the findings in light of their own transfusion experience. In addition, it should be remembered that the study guidelines were pragmatic and acceptable to a large number of centers. The major focus in these guidelines was on hemoglobin levels which do not necessarily reflect tissue oxygenation. Other factors such as the level of erythropoiesis should also be taken into account before deciding whether to transfuse.

Red blood cell transfusions and potentially related morbidities in neonates under 32 weeks' gestation

BACKGROUND

Preterm neonates are likely to require red blood cell (RBC) transfusion, and extremely low birth weight infants almost invariably receive multiple transfusions. Transfusion-reduction strategies can reduce transfusion rates, and might diminish certain adverse outcomes associated with transfusions.

MATERIALS AND METHODS

In a single centre, we retrospectively evaluated RBC transfusion rates among preterm infants ≤32 weeks' gestational age (GA), over a 6-year period before and after adopting national transfusion-reduction strategies. We compared demographic data, adverse events, and outcomes between transfused vs not-transfused neonates. Univariate logistic regression was used to evaluate associations between dichotomous outcomes and number of transfusions, and day of first transfusion. Multivariate logistic regression evaluated the correlation between dichotomous outcomes and transfusion as an independent risk factor.

RESULTS

During the 6 years studied, 181 infants born at ≤32 weeks' GA were admitted to our Neonatal Intensive Care Unit of whom 80 (44%) received at least one RBC transfusion. The transfusion rate tended downwards after adopting transfusion-reduction strategies, reaching 31% in 2018. The reduction was largely due to a marked fall in transfusions of neonates born at 29-32 weeks' GA (p<0.001). The number of transfusions received correlated with odds of having intraventricular haemorrhage (IVH) (OR=1.9; 95% CI: 1.3-2.7; p=0.0001) and the duration of oxygen supplementation (rho=0.51; 95% CI: 0.33-0.66; p≤0.0001). In multivariate logistic regression analysis, transfusion was an independent risk factor for IVH (adjusted OR=7.38; 95% CI: 2.24-24.30; p=0.0001).

DISCUSSION

The application of national, standardised transfusion-reduction strategies was associated with a lower transfusion rate in neonates born at 29-32 weeks' GA, but was less effective among neonates ≤28 weeks, in whom transfusions appeared to be an independent risk factor for severe IVH.

Effect of red blood cell transfusion on short-term outcomes in very low birth weight infants

BACKGROUND

Red blood cell (RBC) transfusion improves cardiorespiratory status of preterm infants by increasing circulating hemoglobin, improving tissue oxygenation, and reducing cardiac output. However, RBC transfusion itself has also been suggested to negatively affect short-term outcomes such as intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), and necrotizing enterocolitis (NEC) in premature infants.

PURPOSE

This study aimed to analyze the relationship between RBC transfusion and short-term outcomes in very low birth weight (VLBW) infants (birth weight, <1,500 g).

METHODS

We retrospectively reviewed the medical records of VLBW infants admitted to the Soonchunhyang University Bucheon Hospital between October 2010 and December 2017. Infants who died during hospitalization were excluded. The infants were divided into 2 groups according to RBC transfusion status. We investigated the relationship between RBC transfusion and short-term outcomes including BPD, ROP, NEC, and IVH.

RESULTS

Of the 250 enrolled VLBW infants, 109 (43.6%) underwent transfusion. Univariate analysis revealed that all shortterm outcomes except early-onset sepsis and patent ductus arteriosus were associated with RBC transfusion. In multivariate analysis adjusted for gestational age, birth weight and Apgar score at 1 minute, RBC transfusion was significantly correlated with BPD (odds ratio [OR], 5.42; P<0.001) and NEC (OR, 3.40; P= 0.009).

CONCLUSION

RBC transfusion is significantly associated with adverse clinical outcomes such as NEC and BPD in VLBW infants. Careful consideration of the patient's clinical condition and appropriate guidelines is required before administration of RBC transfusions.

Management of anaemia in pre-term infants

Pre-term infants have one of the highest transfusion requirements within the hospital-setting. The vast majority of blood transfusions performed in Neonatal Intensive Care Units (NICUs) are for medically stable pre-term infants with anaemia of prematurity, with the aim of improving oxygen delivery to the vital organs during the crucial phase of growth and development. However, despite the frequency of transfusion in this population, the potential benefits and harms of 'top up' transfusion are not fully understood, leading to practice variation between clinicians, institutions and countries. Significant advances have been made in the prevention of anaemia of prematurity, with recent emphasis on optimising infants' circulatory volume at birth via placental transfusion and preserving infants' own blood volume through innovative minimal sampling techniques. More research is urgently needed to establish optimal transfusion thresholds for these high-risk pre-term infants, for whom benefits as well as adverse outcomes may have consequences that extend for decades throughout the recipients' life-course. In this review, we will discuss some of the consensus and controversies regarding optimal management of anaemia in pre-term infants and highlight potential areas for future research.

Blood transfusion for anaemia of prematurity: Current practice in Australia and New Zealand

AIM

To characterise the current transfusion practice among clinicians in Australasian neonatal units and factors that influence their decision-making.

METHODS

Members of the Australia and New Zealand Neonatal Network (ANZNN) and practitioners at their local institutions were invited to participate in a 15-question web-based survey between 1 June and 31 July 2016. The survey was designed to assess (i) haemoglobin-based transfusion thresholds; (ii) presence of local guidelines; (iii) preference for a restrictive or liberal transfusion policy; (iv) perceived benefits and risks of transfusion; and (v) use of clinical adjuncts to assist decision-making.

RESULTS

Overall, 130 participants responded to at least one question. Haemoglobin transfusion thresholds for anaemia of prematurity (AOP) varied significantly from <60 to <120 g/L. Of 103 participants, 36 (35%) reported that they do not have access to local transfusion guidelines. The majority utilise multiple clinical and haematological parameters to guide their decision-making, and approximately half (45/84, 54%) believe that tissue hypoxia detected by near-infrared spectroscopy (NIRS) may better inform transfusion thresholds. Of 102 participants, 51 (50%) support a restrictive rather than liberal transfusion policy. The most commonly reported perceived risks of transfusion for AOP were suppression of endogenous erythropoiesis and increased rates of necrotising enterocolitis.

CONCLUSIONS

There is a significant variation in transfusion practice in Australasian neonatal units. Quality and safety initiatives may assist with improved consistency of transfusion practice across the ANZNN. However, further research is required to better define optimal transfusion thresholds, quantify potential risks of transfusion and determine clinical utility of newer adjuncts such as NIRS.

Use of Placental/Umbilical Blood Sampling for Neonatal Admission Blood Cultures: Benefits, Challenges, and Strategies for Implementation

Placental blood remains an underused resource for early neonatal care despite ample evidence that placental blood provides the same clinical decision making information without the need for painful, invasive blood sampling procedures. Potential benefits of placental/umbilical blood sampling (PUBS) for neonatal admission labs include decreases in pain reactivity, rates of anemia, need for blood transfusions, use of vasopressors, and rates of intraventricular hemorrhage. Here, we present a unique case study of a critically ill infant with contradictory blood culture results from PUBS and direct infant sampling. A negative admission direct sample blood culture result compared with a positive admission PUBS blood culture result suggests that infection may have been missed in the direct infant sample. Relevant placental embryology and circulation is also described, as well as the benefits of PUBS for neonatal admission labs (with focus on the blood culture), challenges associated with PUBS practice, and strategies for implementation of PUBS.

Packed red blood cell transfusions as a risk factor for parenteral nutrition associated liver disease in premature infants

AIM

To determine if packed red blood cell transfusions contribute to the development of parenteral nutrition associated liver disease.

METHODS

A retrospective chart review of 49 premature infants on parenteral nutrition for > 30 d who received packed red blood cell (PRBC) transfusions was performed. Parenteral nutrition associated liver disease was primarily defined by direct bilirubin (db) > 2.0 mg/dL. A high transfusion cohort was defined as receiving > 75 mL packed red blood cells (the median value). Kaplan-Meier plots estimated the median volume of packed red blood cells received in order to develop parenteral nutrition associated liver disease.

RESULTS

Parenteral nutritional associated liver disease (PNALD) was noted in 21 (43%) infants based on db. Among the 27 high transfusion infants, PNALD was present in 17 (64%) based on elevated direct bilirubin which was significantly greater than the low transfusion recipients. About 50% of the infants, who were transfused 101-125 mL packed red blood cells, developed PNALD based on elevation of direct bilirubin. All infants who were transfused more than 200 mL of packed red blood cells developed PNALD. Similar results were seen when using elevation of aspartate transaminase or alanine transaminase to define PNALD.

CONCLUSION

In this retrospective, pilot study there was a statistically significant correlation between the volume of PRBC transfusions received by premature infants and the development of PNALD.

Adverse effects of red blood cell transfusions in neonates: a systematic review and meta-analysis

BACKGROUND

Controversy exists regarding the contribution of blood transfusions to a range of adverse clinical outcomes in neonates. The aim of our systematic review was to identify the broader literature on harmful effects and associations potentially attributable to red blood cell (RBC) transfusions.

STUDY DESIGN AND METHODS

A comprehensive search of MEDLINE (PubMed) and EMBASE was undertaken. Eligible studies included both randomized controlled trials (RCTs) and nonrandomized studies examining the effects of small volume (10-20 mL/kg) RBC transfusions on neonates. Primary outcomes of interest were mortality, chronic lung disease, retinopathy of prematurity, necrotizing enterocolitis, and intraventricular hemorrhage. Two independent authors conducted a review of abstracts and then of full-text article reviews as well as data extraction and quality assessments.

RESULTS

Sixty-one studies were eligible for inclusion, including 16 (26%) randomized studies. The majority of studies were nonrandomized (n = 45; 74%), which included 32 observational studies with and 13 studies without a comparator group. There was no evidence that rates of mortality differed between restrictive and liberal strategies for transfusion (eight RCTs: risk ratio, 1.24; 95% confidence interval, 0.89-1.672, heterogeneity = 0%) or for necrotizing enterocolitis (five RCTs: risk ratio, 1.45; 95% confidence interval, 0.91-2.33; heterogeneity = 0%). A liberal strategy also was not superior to restrictive transfusion practice in the pooled randomized studies for rates of retinopathy of prematurity, chronic lung disease, or intraventricular hemorrhage.

CONCLUSIONS

Statistically significant differences in a range of harmful outcomes between neonates exposed to restrictive and liberal RBC transfusion practice were not found. However, the risks of bias identified in many studies and the lack of consistent reporting and definitions of events limits our conclusions.

Anemia and transfusion in the neonate

Neonatal anemia is a frequent occurrence in neonatal intensive care units. Red blood cell transfusion criteria in case of blood loss are clearly defined but optimal hemoglobin or hematocrit thresholds of transfusion for anemia due to decreased production or increased destruction are less evident. This review focuses on the causes of anemia in the newborn period and the most recent evidence-based treatment options, including transfusion and erythropoiesis-stimulating agents.

Prevention of the anaemia of prematurity

Despite recent advances in neonatal and perinatal medicine, extremely low birth weight infants (ELBW) are at high risk of developing anaemia of prematurity (AOP) requiring packed red blood cell (RBC) transfusions. The benefit of transfusing allogenic RBCs for AOP is a controversial issue, except for disturbances in tissue oxygenation. Although the role of erythropoietin (EPO) in the pathophysiology of AOP is well known, neither early nor late recombinant human EPO therapy alters the number or volume of RBC transfusions. It is also known that one-half of the feto-placental blood volume remains outside the newborn infant's circulation at 30 weeks of gestation if the umbilical cord is clamped immediately. Delayed cord clamping (DCC) and umbilical cord milking (UCM) are the main methods for enhancing placental transfusion. The basic principle of these approaches depends on providing high haemoglobin (Hb) levels to premature infants in the delivery room. The enhancement of placental transfusion clearly results in higher Hb levels at birth, reducing the need for RBC transfusions as well as creating a better haemodynamic status during the initial hours of life. To date, enhancement of placental transfusion in the delivery room by either DCC or UCM seems to be the best preventive measure for AOP. Yet, studies on the associated neurodevelopmental outcomes are insufficient to reach a conclusion. This review summarizes the pathophysiology, treatment and preventative strategies of anaemia of prematurity in light of the current literature.

Why do four NICUs using identical RBC transfusion guidelines have different gestational age-adjusted RBC transfusion rates?

OBJECTIVE

To compare neonatal red blood cell (RBC) transfusion rates in four large Intermountain Healthcare NICUs, all of which adhere to the same RBC transfusion guidelines.

STUDY DESIGN

This retrospective analysis was part of a transfusion-management quality-improvement project. De-identified data included RBC transfusions, clinical and laboratory findings, the anemia-prevention strategies in place in each NICU, and specific costs and outcomes.

RESULT

Of 2389 NICU RBC transfusions given during the 4-year period studied, 98.9 ± 2.1% (mean ± S.D.) were compliant with our transfusion guidelines, with no difference in compliance between any of the four NICUs. However, RBC transfusion rates varied widely between the four, with averages ranging from 4.6 transfusions/1000 NICU days to 21.7/1000 NICU days (P < 0.00001). Gestational age-adjusted transfusion rates were correspondingly discordant (P < 0.00001). The lower-transfusing NICUs had written anemia-preventing guidelines, such as umbilical cord milking at very low birth weight delivery, use of cord blood for admission laboratory studies, and darbepoetin dosing for selected neonates. Rates of Bell stage ⩾ 2 necrotizing enterocolitis and grade ⩾ 3 intraventricular hemorrhage were lowest in the two lower-transfusing NICUs (P < 0.0002 and P < 0.0016). Average pharmacy costs for darbepoetin were $84/dose, with an average pharmacy cost of $269 per transfusion averted. With a cost of $900/RBC transfusion, the anemia-preventing strategies resulted in an estimated cost savings to Intermountain Healthcare of about $6970 per 1000 NICU days, or about $282,300 annually.

CONCLUSION

Using transfusion guidelines has been shown previously to reduce practice variability, lower transfusion rates and diminish transfusion costs. Based on our present findings, we maintain that even when transfusion guidelines are in place and adhered to rigorously, RBC transfusion rates are reduced further if anemia-preventing strategies are also in place.

The effect of red blood cell transfusion on intermittent hypoxemia in ELBW infants

OBJECTIVE

To test the hypothesis that the effect of red blood cell (RBC) transfusion on intermittent hypoxemia (IH) in extremely low birth weight (ELBW) infants is dependent on postnatal age.

STUDY DESIGN

Oxygen saturation of 130 ELBW infants, who required transfusion, was monitored continuously for the first 8 weeks of life. We compared the characteristics of IH (SpO2⩽80% for ⩾4 s and ⩽3 min), 24 h before and both 24 h and 24 to 48 h after each RBC transfusion at three distinct time periods: Epoch 1, 1 to 7 days; Epoch 2, 8 to 28 days; and Epoch 3, >28 days.

RESULT

In Epoch 1, the frequency and severity of IH events were not significantly different before and after transfusion. In both Epochs 2 and 3 there was a decrease in IH frequency and severity 24 h after RBC transfusion that persisted for 48 h. In addition, there was a decrease in the overall time spent with SpO2 ⩽80% which persisted for 24 h after transfusion in Epochs 1 and 3, and for 48 h in Epoch 3.

CONCLUSION

The benefit of RBC transfusion on IH is age dependent as improvement in the frequency and severity of IH after transfusion only occurs beyond the first week of life. These observations will aid clinician's decision making by clarifying the benefit of RBC transfusions on patterns of oxygenation in preterm infants.

Effect of umbilical cord milking on morbidity and survival in extremely low gestational age neonates

OBJECTIVE

Delayed umbilical cord clamping benefits extremely low gestational age neonates (ELGANs) but has not gained wide acceptance. We hypothesized that milking the umbilical cord (MUC) would avoid resuscitation delay but improve hemodynamic stability and reduce rates for composite outcome of severe intraventricular hemorrhage, necrotizing enterocolitis, and/or death before discharge.

STUDY DESIGN

We implemented a joint neonatal/maternal-fetal quality improvement process for MUC starting September 2011. The MUC protocol specified that infants who were born at <30 weeks of gestation undergo MUC 3 times over a duration of <30 seconds at delivery. Obstetric and neonatal data were collected until discharge. We compared the MUC group to retrospective ELGAN cohort delivered at our center between January 2010 and August 2011. Analysis was intention-to-treat.

RESULTS

We identified 318 ELGANs: 158 eligible for MUC and 160 retrospective control neonates. No adverse events were reported with cord milking. There was no difference in neonatal resuscitation, Apgar scores, or admission temperature. Hemodynamic stability was improved in the MUC group with higher mean blood pressures through 24 hours of age, despite less vasopressor use (18% vs 32%; P < .01). The initial hematocrit value was higher (50% vs 45%; P < .01), and red cell transfusions were fewer (57% vs 79%; P < .01) in MUC vs control infants. Presence of the composite outcome was significantly less in MUC vs the historic control infants (22% v 39%; odds ratio, 1.81; 95% confidence interval, 1.06-3.10). There were also reductions in intraventricular hemorrhage, necrotizing enterocolitis, and death before hospital discharge.

CONCLUSION

MUC improves early hemodynamic stability and is associated with lower rates of serious morbidity and death among ELGANs.

Whole-blood viscosity in the neonate: effects of gestational age, hematocrit, mean corpuscular volume and umbilical cord milking

OBJECTIVE

The American College of Obstetrics and Gynecology Committee on Obstetric Practice recently endorsed delayed cord clamping at preterm delivery. However, the committee report expressed the concern by some practitioners that delayed clamping or cord milking might induce hyperviscosity in preterm neonates. To address this issue we: (1) established reference ranges for whole-blood viscosity among preterm neonates (viscosity reference ranges had previously been reported only in term neonates) and (2) determined the effect of umbilical cord milking at deliveries <32 weeks gestation on subsequent blood viscosity measurements.

STUDY DESIGN

This was a prospective study in two Neonatal Intensive Care Units. Blood viscosity was measured using a cone and plate viscometer. Associations were sought with gestation, hematocrit/hemoglobin and mean corpuscular volume. Reference ranges were determined for preterm infants <32 weeks gestation. Then, after umbilical cord milking at deliveries <32 weeks, viscosity was measured at birth and again during the 12 h after birth. In neonates with viscosities >95th % range, we sought signs of hyperviscosity (plethora, hypotonia, hypoglycemia, hyperbilirubinemia, thrombocytopenia).

RESULT

Viscosity at higher and lower sheer rates were linearly related (n=32, r=0.971). Within the range of hematocrits measured (29-63%) viscosity correlated with hematocrit (r=0.877) and hemoglobin (r=0.853) but not with erythrocyte size (r=0.179). Viscosity was related to gestational age (n=58), primarily due to the lower hematocrits at lower gestational ages. In the 12 h after cord milking viscosity ranged from 3.1 to 9.5 centipoise. Three of twenty preterm, neonates had viscosities >95th % reference range. However, all values were well below those where hyperviscosity is defined in term neonates and all lacked features of hyperviscosity.

CONCLUSION

Cord blood viscosity is directly proportional to hematocrit/hemoglobin, lower at early gestation and not associated with erythrocyte size. Cord milking at preterm delivery is associated with a low risk of clinical hyperviscosity. Practioners should not refrain from cord milking at preterm delivery because of a concern that it will commonly cause neonatal hyperviscosity.

Using umbilical cord blood for the initial blood tests of VLBW neonates results in higher hemoglobin and fewer RBC transfusions

OBJECTIVE

We previously described a method for reducing early phlebotomy losses from very low birth weight (VLBW) neonates by obtaining the initial blood tests from otherwise discarded fetal blood from the placenta. In the present study we sought to; (1) measure the feasibility of performing this method in actual practice, (2) test the hypothesis that this method would result in higher hemoglobin concentrations and lower erythrocyte transfusion rates in the first week after birth.

METHODS

We conducted two studies in three Intermountain Healthcare NICUs. The first was a feasibility analysis involving 96 VLBW neonates, measuring the success of obtaining the NICU admission laboratory blood tests this way. The second study used case-control methodology to test the hypothesis that this method would result in a higher blood hemoglobin 12 to 24 h after birth, and a lower proportion receiving an erythrocyte transfusion in the first week.

RESULT

In 91 of 96 VLBW neonates (95%) the initial blood tests were successfully obtained with this method. The success rate was not diminished by delayed cord clamping or cord milking, as it was successful in 35 of 36 (97%) such instances. Cases and controls were well matched on demographic and level of illness comparisons. Among cases the hemoglobin generally increased between birth and 12 to 24 h later, but among controls the hemoglobin generally decreased (P<0.05). In the week following birth fewer cases received vasopressors (P<0.01) and erythrocyte transfusions (P<0.001).

CONCLUSION

We judge that it is feasible to collect the initial blood tests of VLBW neonates using otherwise discarded umbilical cord/placental blood, in that this can be accomplished in about 95% of VLBW deliveries. This method, which can be used in addition to either delayed clamping of the umbilical cord or cord milking, results in higher hemoglobin concentrations, less vasopressor use and fewer transfusions in the first week.